'Paint-on' laser seeks to free chip bottlenecks

MANHASSET, N.Y.  Researchers at the University of Toronto have created a laser that promises to relieve the interconnect bottleneck in microchips.

Scientists believe the laser would make it possible to form interconnections within chips using infrared light. This would help answer some concerns that current-generation microchips would reach their practical capacity sometime around 2010.

The laser is not a laser in the traditional sense of the word. Instead, it takes on the form of colloidal quantum dots—nanometer sized particles of semiconductor that are suspended in a solvent, according to the researchers.

The scientists, from the University of Toronto’s Dept. of Electrical and Computer Engineering, published a study describing the laser in the April 17 issue of the journal Optics Express.

According to one of the researchers, Professor Ted Sargent, a small vial of paint carried in his briefcase is used to make the laser.

"We've made a laser that can be smeared onto another material," said Sargent, a Canada Research Chair in Nanotechnology "This is the first paint-on semiconductor laser to produce the invisible colors of light needed to carry information through fiber-optics. The infrared light could, in the future, be used to connect microprocessors on a silicon computer chip."

According to Sjoerd Hoogland, a post-doctoral fellow and the first author of the paper, "This laser could help us to keep feeding the information-hungry Internet generation."

The laser's most remarkable feature was its simplicity. "I made the laser by dipping a miniature glass tube in the paint and then drying it with a hairdryer," he said. "Once the right nanoparticles are made, the procedure takes about five minutes."

The microchip industry is looking for components that exist on the scale of transistors and are made of semiconductors, which would produce light when exposed to electrical current. With this development, it could be possible to use the electronics already found on microchips to power a laser that communicates within the chip itself.

"We crystallized precisely the size of the nanoparticles that would tune the color of light coming from the laser. We chose nanoparticle size, and thus color, the way a guitarist chooses frets to select the pitch of the instrument," Hoogland said. "Optical data transfer relies on light in the infrared--beams of light 1.5 micrometers in wavelength travel farthest in glass. We made our particles just the right size to generate laser light at exactly this wavelength."